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Nirendra Nath Mustafi: Application of ImageJ in characterization of particulate matter emissions from diesel engine

Abstract

The main emphasis of this work was to investigate experimentally the particulate matter (PM) emissions from a dual fuel engine operated on alternative gaseous fuels such as natural gas and simulated biogas in comparison to the diesel fueling. A number of techniques were employed to determine and characterize the PM emissions from the dual fuel engine in this study. For the PM size distribution and morphological studies, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used. In order to quantify the results obtained from SEM and TEM images, a public domain image processing software package, ImageJ, Version 1.38l, (National Institue of Health, NIH) was used. This software allows analysis of PM samples for the structural properties of the agglomerated particles. ImageJ measured area, mean, standard deviation, min and max of selection or entire image. The program measured lengths, widths, center of mass and angles of the selected area in an image. All the images obtained in SEM examination, were saved in TIFF format and opened and processed one by one using ImageJ. The saved images were of 8-bit black and white with a non-homogeneous contrast. The image is made up of pixels which are essentially dots with given intensity or greyscale value and integer in the range 0 (black) to 255 (white). ImageJ with adjusted brightness/contrast and thresholded detects either the black or white objects. An important tool of ImageJ is ‘Threshold’ which interactively sets lower and upper threshold values, segmenting the image into target objects and background. Pixels with brightness greater than or equal to the lower threshold and less than or equal to the upper threshold are normally displayed in red (i.e. detected by ImageJ). The very first step of image processing was to calibrate the image according to the scale bar displayed on images which converted the pixels to the known distance (i.e. scale bar) with the known units (such as micrometer or nanometer). ‘Analyze Particles’ tool and suitable plugins of ImageJ were employed to analyze the detected areas (or particulates) such as counting, measuring area and perimeter, fitting best-fit ellipses or measuring maximum projected length and width of the particulates. Result files were generated where all the numerical values were tabulated. These results included: the number of particulates, their measured areas and perimeters, lengths of minor and major axes of the best-fitted ellipses, maximum projected length (Lmax) and maximum width (Wmax) of the agglomerates. All the generated images and result files were saved separately and the result files were opened in Excel and statistical analysis was performed afterwards.

Keywords

Diesel engine, Particulate matter, Emissions, Electron microscopy, ImageJ

Administrative data

Presenting author: Nirendra Nath Mustafi
Organisation: Rajshahi University of Engineering & Technology, Rajshahi 6204, Bangladesh

co-authors: Robert Roy Raine

Department of Mechanical Engineering

The University of Auckland, Auckland, New Zealand

Bryony James

Department of Chemical and Materials Engineering

The University of Auckland, Auckland, New Zealand

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